The present invention relates generally to force feedback and, in particular, to a family of haptic interface devices which exploit multiple redundant links to position a scribe or stylus in space.
Force feedback devices originated in various specialized ways in the 1960s with teleoperations. Most of these devices were xe2x80x9creplicaxe2x80x9d devices, wherein a smaller controlling or master robot was moved by an operator to control movement of a larger slaved robot. Forces detected at the slave were then also fed back to the operator through the master robot""s actuators. Such prior art is substantially described in U.S. Pat. No. 5,389,865 to Jacobus et al.
In the late 1980s, NASA funded several experiments using force feedback devices which were not configured as having identical versions of a slave device. This was important at the time because an astronaut may want to control a number of kinds of space-based robots and cranes from one xe2x80x9cuniversalxe2x80x9d controller. To make this universal controller concept work, the master controller was connected logically to the slave through a network of computers which were capable of translating the master kinematics typically into Cartesian coordinates and from Cartesian to slave kinematics and back the other way.
Once this computer controller is in place on the master side of the system, it becomes possible to send inputs from the master (joystick, wheel, yoke, etc.) to a simulated slave rather than a real one, and to accept forces from the simulation for application to the master as well. This is one innovation described in U.S. Pat. Nos. 5,389,865 and 5,459,382 to Jacobus et al. As disclosed by Jacobus, this simulation need not be a real device, like a crane or robot, but may be a simulated automobile, boat, plane, or weapon. It can even be a simulation of a person performing tasks in a virtual world, such as walking, handling things, touching surfaces.
U.S. Patents Nos. 5,459,382 and 5,389,865 describe an early device and method for providing users with a touch or tactile interface into a virtual world which allows the user to touch virtual objects, or objects which are not real, but rather are described by a model which resides inside a computer system. U.S. Pat. Nos. 5,389,865 and 5,629,594, and U.S. application Ser. No. 08/845,375 on these devices and the software architecture responsible for expressing abstract virtual models in the computer as forces created based on the position of the devices. U.S. application Ser. No. 08/861,080 describes in detail how a software architecture represents abstract virtual objects in terms of superpositions of virtual geometrical entities and dynamic special xe2x80x9cfeelxe2x80x9d effects. U.S. application Ser. No. 08/859,877 describes how virtual objects and geometrical entities are built using CAD/CAM and geometrical design methods. U.S. application Ser. No. 08/859,157 describes how touch or haptic attributes are parameterized and represented using graphical user interface elements. All of the patents and applications discussed above are set forth herein in their entirety by reference.
Broadly, this invention resides in techniques and systems for combining tactile feedback elements to create a family of haptic or touch user interface devices. In particular, these combinations exploit multiple redundant links to position a scribe or stylus in a single, unique multi-degree of freedom position and orientation while presenting a force or force and torque to the stylus. The stylus, in turn, is pressed on the CAD/CAM or designer""s hand, simulating tactile interaction with a virtual object within the device""s volume of movement.
In a basic configuration, a haptic pointing device according to the invention includes a plurality of rigid, elongated proximal members, each connected to a separate rigid, elongated distal member through an articulating joint. The other ends of each proximal member is coupled to an actuator causing that member to swing within a separate plane in response to a control signal. An end-effector is interconnected to the second end of each distal member through an articulating joint, such that as the actuators move the proximal members, the end-effector moves in space. The various articulating joints may be universal joints, ball joints, of composed of a flexible material.
In a preferred embodiment, the device includes three proximal members and three distal members, enabling the end effector to move in three-dimensional space. The actuators preferably take the form of motors having a shaft perpendicular to the plane of movement of the proximal member coupled thereto. Different style motors, including pancake motors, may be used. In one configuration, the end-effector is coupled to a user-graspable element having a preferred orientation in space, with the arrangement of the members and joints being such that the element retains the preferred orientation as the end effector is moved by the actuators.
In a force-feedback application, the haptic pointing device further includes a position sensor associated with each proximal member, and haptic processing means operative to output an electronic signal indicative of the position of the end-effector in space, and receive an electronic signal causing the actuators to move the end-effector to a point in space. The haptic processing means may in turn be interfaced to a virtual reality system including descriptions of virtual objects, enabling a user to interact with the objects through the end effector. Alternatively, the haptic processing means may be interfaced to a slave system including a separate set of actuators and encoders, enabling a user to interact with the objects through the end effector as part of a teleoperations environment.
In alternative embodiments, additional components may be provided to increase flexibility, degrees of freedom, or both. For instance, the end-effector may be further coupled to a user-graspable element such as a handle or stylus to provide one or more additional degrees of freedom associated with roll, pitch and yaw. The system may include a pair of base platforms, each with its own set of actuated proximal and distal members for example, six sets of proximal and distal members may be utilized, three sets associated with each of the two base platforms. In all cases, the system may further conveniently include a docking station to receive the end effector for calibration purposes.